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Cadmium uptake and translocation in seedlings of near isogenic lines of durum wheat that differ in grain cadmium accumulation.

Harris NS, Taylor GJ - BMC Plant Biol. (2004)

Bottom Line: In short-term studies (<3 h) using 109Cd-labelled nutrient solutions, there were no differences between lines in time- or concentration-dependent 109Cd accumulation by roots.There were no differences between the lines in 65Zn accumulation or partitioning that could account for the difference between lines in 109Cd translocation.These results suggest that restricted root-to-shoot Cd translocation may limit Cd accumulation in durum wheat grain by directly controlling Cd translocation from roots during grain filling, or by controlling the size of shoot Cd pools that can be remobilised to the grain.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada. nsharris@ualberta.ca

ABSTRACT

Background: Cadmium (Cd) concentrations in durum wheat (Triticum turgidum L. var durum) grain grown in North American prairie soils often exceed proposed international trade standards. To understand the physiological processes responsible for elevated Cd accumulation in shoots and grain, Cd uptake and translocation were studied in seedlings of a pair of near-isogenic durum wheat lines, high and low for Cd accumulation in grain.

Results: In short-term studies (<3 h) using 109Cd-labelled nutrient solutions, there were no differences between lines in time- or concentration-dependent 109Cd accumulation by roots. In contrast, rates of 109Cd translocation from roots to shoots following longer exposure (48-60 h) were 1.8-fold higher in the high Cd-accumulating line, despite equal whole-plant 109Cd accumulation in the lines. Over the same period, the 109Cd concentration in root-pressure xylem exudates was 1.7 to 1.9-fold higher in the high Cd-accumulating line. There were no differences between the lines in 65Zn accumulation or partitioning that could account for the difference between lines in 109Cd translocation.

Conclusion: These results suggest that restricted root-to-shoot Cd translocation may limit Cd accumulation in durum wheat grain by directly controlling Cd translocation from roots during grain filling, or by controlling the size of shoot Cd pools that can be remobilised to the grain.

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Related in: MedlinePlus

Long-term 65Zn accumulation in durum wheat seedlings. Time-course of 65Zn accumulation in intact roots (A), 65Zn translocation to shoots (B), and 65Zn accumulation per plant (C) of high (TL-H) and low (TL-L) Cd-accumulating isolines of durum wheat. Roots of 6-d old seedlings were exposed for up to 60 h (solutions changed every 12 h) in 15 mL of complete nutrient solution containing 50 pM 109Cd and 0.5 μM 65Zn. Desorbable 65Zn was removed following treatment by a 30 min (2°C) wash in non-radiolabelled nutrient solution containing 50 μM DTPA. Inset shows desorbable 65Zn expressed as a percentage of total 65Zn accumulation in the roots. Means and standard errors of 7 replicates (3 plants per replicate) are plotted.
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Figure 7: Long-term 65Zn accumulation in durum wheat seedlings. Time-course of 65Zn accumulation in intact roots (A), 65Zn translocation to shoots (B), and 65Zn accumulation per plant (C) of high (TL-H) and low (TL-L) Cd-accumulating isolines of durum wheat. Roots of 6-d old seedlings were exposed for up to 60 h (solutions changed every 12 h) in 15 mL of complete nutrient solution containing 50 pM 109Cd and 0.5 μM 65Zn. Desorbable 65Zn was removed following treatment by a 30 min (2°C) wash in non-radiolabelled nutrient solution containing 50 μM DTPA. Inset shows desorbable 65Zn expressed as a percentage of total 65Zn accumulation in the roots. Means and standard errors of 7 replicates (3 plants per replicate) are plotted.

Mentions: In contrast to 109Cd, there were no significant differences in 65Zn partitioning between the two isolines (F1,84 < 0.01, p = 0.947; Table 2). Similarly, there were no significant differences between isolines for 65Zn accumulation in shoots (F1,84 = 1.81, p = 0.182; Figure 7B) or whole plants (F1,84 = 2.94, p = 0.090; Figure 7C). Long-term 65Zn accumulation in roots (Figure 7A) was slightly higher in TL-L than in TL-H (F1,84 = 7.64, p = 0.007).


Cadmium uptake and translocation in seedlings of near isogenic lines of durum wheat that differ in grain cadmium accumulation.

Harris NS, Taylor GJ - BMC Plant Biol. (2004)

Long-term 65Zn accumulation in durum wheat seedlings. Time-course of 65Zn accumulation in intact roots (A), 65Zn translocation to shoots (B), and 65Zn accumulation per plant (C) of high (TL-H) and low (TL-L) Cd-accumulating isolines of durum wheat. Roots of 6-d old seedlings were exposed for up to 60 h (solutions changed every 12 h) in 15 mL of complete nutrient solution containing 50 pM 109Cd and 0.5 μM 65Zn. Desorbable 65Zn was removed following treatment by a 30 min (2°C) wash in non-radiolabelled nutrient solution containing 50 μM DTPA. Inset shows desorbable 65Zn expressed as a percentage of total 65Zn accumulation in the roots. Means and standard errors of 7 replicates (3 plants per replicate) are plotted.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC404425&req=5

Figure 7: Long-term 65Zn accumulation in durum wheat seedlings. Time-course of 65Zn accumulation in intact roots (A), 65Zn translocation to shoots (B), and 65Zn accumulation per plant (C) of high (TL-H) and low (TL-L) Cd-accumulating isolines of durum wheat. Roots of 6-d old seedlings were exposed for up to 60 h (solutions changed every 12 h) in 15 mL of complete nutrient solution containing 50 pM 109Cd and 0.5 μM 65Zn. Desorbable 65Zn was removed following treatment by a 30 min (2°C) wash in non-radiolabelled nutrient solution containing 50 μM DTPA. Inset shows desorbable 65Zn expressed as a percentage of total 65Zn accumulation in the roots. Means and standard errors of 7 replicates (3 plants per replicate) are plotted.
Mentions: In contrast to 109Cd, there were no significant differences in 65Zn partitioning between the two isolines (F1,84 < 0.01, p = 0.947; Table 2). Similarly, there were no significant differences between isolines for 65Zn accumulation in shoots (F1,84 = 1.81, p = 0.182; Figure 7B) or whole plants (F1,84 = 2.94, p = 0.090; Figure 7C). Long-term 65Zn accumulation in roots (Figure 7A) was slightly higher in TL-L than in TL-H (F1,84 = 7.64, p = 0.007).

Bottom Line: In short-term studies (<3 h) using 109Cd-labelled nutrient solutions, there were no differences between lines in time- or concentration-dependent 109Cd accumulation by roots.There were no differences between the lines in 65Zn accumulation or partitioning that could account for the difference between lines in 109Cd translocation.These results suggest that restricted root-to-shoot Cd translocation may limit Cd accumulation in durum wheat grain by directly controlling Cd translocation from roots during grain filling, or by controlling the size of shoot Cd pools that can be remobilised to the grain.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada. nsharris@ualberta.ca

ABSTRACT

Background: Cadmium (Cd) concentrations in durum wheat (Triticum turgidum L. var durum) grain grown in North American prairie soils often exceed proposed international trade standards. To understand the physiological processes responsible for elevated Cd accumulation in shoots and grain, Cd uptake and translocation were studied in seedlings of a pair of near-isogenic durum wheat lines, high and low for Cd accumulation in grain.

Results: In short-term studies (<3 h) using 109Cd-labelled nutrient solutions, there were no differences between lines in time- or concentration-dependent 109Cd accumulation by roots. In contrast, rates of 109Cd translocation from roots to shoots following longer exposure (48-60 h) were 1.8-fold higher in the high Cd-accumulating line, despite equal whole-plant 109Cd accumulation in the lines. Over the same period, the 109Cd concentration in root-pressure xylem exudates was 1.7 to 1.9-fold higher in the high Cd-accumulating line. There were no differences between the lines in 65Zn accumulation or partitioning that could account for the difference between lines in 109Cd translocation.

Conclusion: These results suggest that restricted root-to-shoot Cd translocation may limit Cd accumulation in durum wheat grain by directly controlling Cd translocation from roots during grain filling, or by controlling the size of shoot Cd pools that can be remobilised to the grain.

Show MeSH
Related in: MedlinePlus